1. Field
One embodiment of the present invention relates to a method of manufacturing a stamper to be used to produce a large number of information recording media by transferring patterns by, e.g., injection molding or imprinting.
2. Description of the Related Art
Recently, the recording capacity of an information recording apparatus is increased by increasing the recording density of a magnetic recording medium. As a magnetic recording medium having a high recording density, a discrete track recording (DTR) magnetic recording medium having patterns including a magnetic portion and nonmagnetic portion on, e.g., a plurality of concentric data recording tracks is known.
As a method of manufacturing a magnetic recording medium like this, nanoimprinting or injection molding using a nickel (Ni) stamper as a metal mold as disclosed in, e.g., Jpn. Pat. Appln. KOKAI Publication No. 2008-12705 is used.
As the recording density of the DTR magnetic recording medium increases, a stamper for use in the manufacture of the medium is requiring a micropatterning technique that forms three-dimensional patterns having a track pitch of, e.g., 100 nm or less.
When the density increases as the track pitch of the three-dimensional patterns decreases, however, the thickness of a resist layer for electron beam (EB) lithography decreases by EB lithography rate control because the lithography performance improves as the resist layer thickness decreases. This sometimes decreases the difference between the projections and recesses on the manufactured master. When using this stamper having a small difference between the projections and recesses, the three-dimensional patterns of a resist mask on a medium may become defective owing to insufficient transfer during imprinting. Also, a sufficiently wide medium projection is necessary for a narrow pitch in order to maintain the write/read performance for the projection. Therefore, finer recess patterns must be written by EB. However, the limit of an EB lithography system makes grooves of a few nm difficult to write. This makes it impossible to obtain a high-density master in the future.
The present invention has been made in consideration of the above situation, and has as its object to manufacture a stamper capable of transferring three-dimensional patterns without any defect, and having high durability.